DETERMINANTE DE COMPOSIÇÃO DE CONSELHO DE ADMINISTRAÇÃO EM PEQUENAS E MÉDIAS EMPRESAS DE SOCIEDADE ANÔNIMA DE CAPITAL FECHADO DA REGIÃO DO ABC

O principal objetivo deste estudo é analisar os determinantes de composição de Conselho de Administração em pequenas e médias empresas de sociedade anônima de capital fechado da região do ABC paulista. A razão de iniciar este trabalho, surgiu devido à constatação de que no Brasil existem poucos artigos e dissertações que tratam de composição de Conselho e os elaborados no exterior se centralizaram na composição em termos de tamanho e tipos de diretores, de desempenho financeiro, de independência etc., mas nenhum deles focou nas determinantes de composição de pequena e média empresa. Portanto, baseando-se nas observações acima, se efetuou pesquisa de campo para responder à seguinte problemática Que determinante(s) estabelece(m) a composição de Conselho de Administração de Pequenas e Médias Empresas de Sociedade Anônima de Empresas da Região do ABC paulista? Partindo dessa problemática, se estabeleceu as seguintes hipóteses: se o poder e a influência do CEO/Presidente do Conselho em empresas de pequeno e médio porte são grandes, então existem baixas possibilidades de ter Conselheiros Externos; se houver segregação de cargos entre o CEO e o Presidente do Conselho e o CEO estiver interessado em preservar a sua atuação, então há probabilidade de escolher Conselheiros Internos; se houver segregação de cargos entre o CEO e o Presidente do Conselho e o CEO estiver interessado na eficiência, orientação e na necessidade de recursos externos, então há probabilidade de escolher Conselheiros Externos; se a empresa está no Ciclo de Vida Expansão e Maturidade- , então há possibilidades de adotarem Conselheiros Externos.(AU)

Systematic derivation of partition functions for ligand binding to two-dimensional lattices

The Ising problem consists in finding the analytical solution of the partition function of a lattice once the interaction geometry among its elements is specified. No general analytical solution is available for this problem, except for the one-dimensional case. Using site-specific thermodynamics, it is shown that the partition function for ligand binding to a two-dimensional lattice can be obtained from those of one-dimensional lattices with known solution. The complexity of the lattice is reduced recursively by application of a contact transformation that involves a relatively small number of steps. The transformation implemented in a computer code solves the partition function of the lattice by operating on the connectivity matrix of the graph associated with it. This provides a powerful new approach to the Ising problem, and enables a systematic analysis of two-dimensional lattices that model many biologically relevant phenomena. Application of this approach to finite two-dimensional lattices with positive cooperativity indicates that the binding capacity per site diverges as Na (N = number of sites in the lattice) and experiences a phase-transition-like discontinuity in the thermodynamic limit N → ∞. The zeroes of the partition function tend to distribute on a slightly distorted unit circle in complex plane and approach the positive real axis already for a 5×5 square lattice. When the lattice has negative cooperativity, its properties mimic those of a system composed of two classes of independent sites with the apparent population of low-affinity binding sites increasing with the size of the lattice, thereby accounting for a phenomenon encountered in many ligand-receptor interactions.

Invariance of brain-wave representations of simple visual images and their names

In two experiments, electric brain waves of 14 subjects were recorded under several different conditions to study the invariance of brain-wave representations of simple patches of colors and simple visual shapes and their names, the words blue, circle, etc. As in our earlier work, the analysis consisted of averaging over trials to create prototypes and test samples, to both of which Fourier transforms were applied, followed by filtering and an inverse transformation to the time domain. A least-squares criterion of fit between prototypes and test samples was used for classification. The most significant results were these. By averaging over different subjects, as well as trials, we created prototypes from brain waves evoked by simple visual images and test samples from brain waves evoked by auditory or visual words naming the visual images. We correctly recognized from 60% to 75% of the test-sample brain waves. The general conclusion is that simple shapes such as circles and single-color displays generate brain waves surprisingly similar to those generated by their verbal names. These results, taken together with extensive psychological studies of auditory and visual memory, strongly support the solution proposed for visual shapes, by Bishop Berkeley and David Hume in the 18th century, to the long-standing problem of how the mind represents simple abstract ideas.

Absence of a barrier to backwards rotation of the bacterial flagellar motor demonstrated with optical tweezers

A cell of the bacterium Escherichia coli was tethered covalently to a glass coverslip by a single flagellum, and its rotation was stopped by using optical tweezers. The tweezers acted directly on the cell body or indirectly, via a trapped polystyrene bead. The torque generated by the flagellar motor was determined by measuring the displacement of the laser beam on a quadrant photodiode. The coverslip was mounted on a computer-controlled piezo-electric stage that moved the tether point in a circle around the center of the trap so that the speed of rotation of the motor could be varied. The motor generated ≈4500 pN nm of torque at all angles, regardless of whether it was stalled, allowed to rotate very slowly forwards, or driven very slowly backwards. This argues against models of motor function in which rotation is tightly coupled to proton transit and back-transport of protons is severely limited.

A host-specific function is required for ligation of a wide variety of ribozyme-processed RNAs

Hepatitis δ virus (HDV) replicates its circular RNA genome via a rolling circle mechanism. During this process, cis-acting ribozymes cleave adjacent upstream sequences and thereby resolve replication intermediates to unit-length RNA. The subsequent ligation of these 5′OH and 2′,3′-cyclic phosphate termini to form circular RNA is an essential step in the life cycle of the virus. Here we present evidence for the involvement of a host activity in the ligation of HDV RNA. We used both HDV and hammerhead ribozymes to generate a panel of HDV and non-HDV RNA substrates that bear 5′ hydroxyl and 2′,3′- cyclic phosphate termini. We found that ligation of these substrates occurred in host cells, but not in vitro or in Escherichia coli. The host-specific ligation activity was capable of joining RNA in both bimolecular and intramolecular reactions and functioned in a sequence-independent manner. We conclude that mammalian cells contain a default pathway that efficiently circularizes ribozyme processed RNAs. This pathway could be exploited in the delivery of stable antisense and decoy RNA to the nucleus.

Precisely full length, circularizable, complementary RNA: An infectious form of potato spindle tuber viroid

The replication of many viral and subviral pathogens as well as the amplification of certain cellular genes proceeds via a rolling circle mechanism. For potato spindle tuber (PSTVd) and related viroids, the possible role of a circular (−)strand RNA as a template for synthesis of (+)strand progeny is unclear. Infected plants appear to contain only multimeric linear (−)strand RNAs, and attempts to initiate infection with multimeric (−)PSTVd RNAs generally have failed. To examine critically the infectivity of monomeric (−)strand viroid RNAs, we have developed a ribozyme-based expression system for the production of precisely full length (−)strand RNAs whose termini are capable of undergoing facile circularization in vitro. Mechanical inoculation of tomato seedlings with electrophoretically purified (−)PSTVd RNA led to a small fraction of plants becoming infected whereas parallel assays with an analogous tomato planta macho viroid (−)RNA resulted in a much larger fraction of infected plants. Ribozyme-mediated production of (−)PSTVd RNA in transgenic plants led to the appearance of monomeric circular (−)PSTVd RNA and large amounts of (+)PSTVd progeny. No monomeric circular (−)PSTVd RNA could be detected in naturally infected plants by using either ribonuclease protection or electrophoresis under partially denaturing conditions. Although not a component of the normal replicative pathway, precisely full length (−)PSTVd RNA appears to contain all of the structural and regulatory elements necessary for initiation of viroid replication.

An alteration in concatameric structure is associated with efficient segregation of plasmids in transfected Plasmodium falciparum parasites

Transfection of the human malaria parasite Plasmodium falciparum is currently performed with circularised plasmids that are maintained episomally in parasites under drug selection but which are rapidly lost when selection pressure is removed. In this paper, we show that in instances where gene targeting is not favoured, transfected plasmids can change to stably replicating forms (SRFs) that are maintained episomally in the absence of drug selection. SRF DNA is a large concatamer of the parental plasmid comprising at least nine plasmids arranged in a head-to-tail array. We show as well that the original unstable replicating forms (URFs) are also present as head-to-tail concatamers, but only comprise three plasmids. Limited digestion and γ irradiation experiments revealed that while URF concatamers are primarily circular, as expected, SRF concatamers form a more complex structure that includes extensive single-stranded DNA. No evidence of sequence rearrangement or additional sequence was detected in SRF DNA, including in transient replication experiments designed to select for more efficiently replicating plasmids. Surprisingly, these experiments revealed that the bacterial plasmid alone can replicate in parasites. Together, these results imply that transfected plasmids are required to form head-to-tail concatamers to be maintained in parasites and implicate both rolling-circle and recombination-dependent mechanisms in their replication.

An RNA topoisomerase.

A synthetic strand of RNA has been designed so that it can adopt two different topological states (a circle and a trefoil knot) when ligated into a cyclic molecule. The RNA knot and circle have been characterized by their behavior in gel electrophoresis and sedimentation experiments. This system allows one to assay for the existence of an RNA topoisomerase, because the two RNA molecules can be inter-converted only by a strand passage event. We find that the interconversion of these two species can be catalyzed by Escherichia coli DNA topoisomerase III, indicating that this enzyme can act as an RNA topoisomerase. The conversion of circles to knots is accompanied by a small amount of RNA catenane generation. These findings suggest that strand passage must be considered a potential component of the folding and modification of RNA structures.

The old problems of glass and the glass transition, and the many new twists.

In this paper I review the ways in which the glassy state is obtained both in nature and in materials science and highlight a "new twist"--the recent recognition of polymorphism within the glassy state. The formation of glass by continuous cooling (viscous slowdown) is then examined, the strong/fragile liquids classification is reviewed, and a new twist-the possibility that the slowdown is a result of an avoided critical point-is noted. The three canonical characteristics of relaxing liquids are correlated through the fragility. As a further new twist, the conversion of strong liquids to fragile liquids by pressure-induced coordination number increases is demonstrated. It is then shown that, for comparable systems, it is possible to have the same conversion accomplished via a first-order transition within the liquid state during quenching. This occurs in the systems in which "polyamorphism" (polymorphism in the glassy state) is observed, and the whole phenomenology is accounted for by Poole's bond-modified van der Waals model. The sudden loss of some liquid degrees of freedom through such weak first-order transitions is then related to the polyamorphic transition between native and denatured hydrated proteins, since the latter are also glass-forming systems--water-plasticized, hydrogen bond-cross-linked chain polymers (and single molecule glass formers). The circle is closed with a final new twist by noting that a short time scale phenomenon much studied by protein physicists-namely, the onset of a sharp change in d/dT ( is the Debye-Waller factor)--is general for glass-forming liquids, including computer-simulated strong and fragile ionic liquids, and is closely correlated with the experimental glass transition temperature. The latter thus originates in strong anharmonicity in certain components of the vibrational density of states, which permits the system to access the multiple minima of its configuration space. The connection between the anharmonicity in these modes, vibrational localization, the Kauzmann temperature, and the fragility of the liquid is proposed as the key problem in glass science.

Interaction with the recombination hot spot chi in vivo converts the RecBCD enzyme of Escherichia coli into a chi-independent recombinase by inactivation of the RecD subunit.

The RecBCD enzyme of Escherichia coli promotes recombination preferentially at chi nucleotide sequences and has in vivo helicase and strong duplex DNA exonuclease (exoV) activities. The enzyme without the RecD subunit, as in a recD null mutant, promotes recombination efficiently but independently of chi and has no nucleolytic activity. Employing phage lambda red gam crosses, phage T4 2- survival measurements, and exoV assays, it is shown that E. coli cells in which RecBCD has extensive opportunity to interact with linear chi-containing DNA (produced by rolling circle replication of a plasmid with chi or by bleomycin-induced fragmentation of the cellular chromosome) acquire the phenotype of a recD mutant and maintain this for approximately 2 h. It is concluded that RecBCD is converted into RecBC during interaction with chi by irreversible inactivation of RecD. After conversion, the enzyme is released and initiates recombination on other DNA molecules in a chi-independent fashion. Overexpression of recD+ (from a plasmid) prevented the phenotypic change and providing RecD after the change restored chi-stimulated recombination. The observed recA+ dependence of the downregulation of exoV could explain the previously noted "reckless" DNA degradation of recA mutants. It is proposed that chi sites are regulatory elements for the RecBCD to RecBC switch and thereby function as cis- and trans-acting stimulators of RecBC-dependent recombination.

Rolling replication of short DNA circles.

Natural genes and proteins often contain tandemly repeated sequence motifs that dramatically increase physiological specificity and activity. Given the selective value of such repeats, it is likely that several different mechanisms have been responsible for their generation. One mechanism that has been shown to generate relatively long tandem repeats (in the kilobase range) is rolling circle replication. In this communication, we demonstrate that rolling circle synthesis in a simple enzymatic system can produce tandem repeats of monomers as short as 34 bp. In addition to suggesting possible origins for natural tandem repeats, these observations provide a facile means for constructing libraries of repeated motifs for use in "in vitro evolution" experiments designed to select molecules with defined biological or chemical properties.

In vitro cleavage and joining at the viral origin of replication by the replication initiator protein of tomato yellow leaf curl virus.

Replication of the single-stranded DNA genome of geminiviruses occurs via a double-stranded intermediate that is subsequently used as a template for rolling-circle replication of the viral strand. Only one of the proteins encoded by the virus, here referred to as replication initiator protein (Rep protein), is indispensable for replication. We show that the Rep protein of tomato yellow leaf curl virus initiates viral-strand DNA synthesis by introducing a nick in the plus strand within the nonanucleotide 1TAATATT decreases 8AC, identical among all geminiviruses. After cleavage, the Rep protein remains bound to the 5' end of the cleaved strand. In addition, we show that the Rep protein has a joining activity, suggesting that it acts as a terminase, thus resolving the nascent viral single strand into genome-sized units.

Innovative analytical strategies for the development of sensor devices and mass spectrometry methods

Il lavoro presentato in questa tesi di Dottorato è incentrato sullo sviluppo di strategie analitiche innovative basate sulla sensoristica e su tecniche di spettrometria di massa in ambito biologico e della sicurezza alimentare. Il primo capitolo tratta lo studio di aspetti metodologici ed applicativi di procedure sensoristiche per l’identificazione e la determinazione di biomarkers associati alla malattia celiaca. In tale ambito, sono stati sviluppati due immunosensori, uno a trasduzione piezoelettrica e uno a trasduzione amperometrica, per la rivelazione di anticorpi anti-transglutaminasi tissutale associati a questa malattia. L’innovazione di questi dispositivi riguarda l’immobilizzazione dell’enzima tTG nella conformazione aperta (Open-tTG), che è stato dimostrato essere quella principalmente coinvolta nella patogenesi. Sulla base dei risultati ottenuti, entrambi i sistemi sviluppati si sono dimostrati una valida alternativa ai test di screening attualmente in uso per la diagnosi della celiachia. Rimanendo sempre nel contesto della malattia celiaca, ulteriore ricerca oggetto di questa tesi di Dottorato, ha riguardato lo sviluppo di metodi affidabili per il controllo di prodotti “gluten-free”. Il secondo capitolo tratta lo sviluppo di un metodo di spettrometria di massa e di un immunosensore competitivo per la rivelazione di prolammine in alimenti “gluten-free”. E’ stato sviluppato un metodo LC-ESI-MS/MS basato su un’analisi target con modalità di acquisizione del segnale selected reaction monitoring per l’identificazione di glutine in diversi cereali potenzialmente tossici per i celiaci. Inoltre ci si è focalizzati su un immunosensore competitivo per la rivelazione di gliadina, come metodo di screening rapido di farine. Entrambi i sistemi sono stati ottimizzati impiegando miscele di farina di riso addizionata di gliadina, avenine, ordeine e secaline nel caso del sistema LC-MS/MS e con sola gliadina nel caso del sensore. Infine i sistemi analitici sono stati validati analizzando sia materie prime (farine) che alimenti (biscotti, pasta, pane, etc.). L’approccio sviluppato in spettrometria di massa apre la strada alla possibilità di sviluppare un test di screening multiplo per la valutazione della sicurezza di prodotti dichiarati “gluten-free”, mentre ulteriori studi dovranno essere svolti per ricercare condizioni di estrazione compatibili con l’immunosaggio competitivo, per ora applicabile solo all’analisi di farine estratte con etanolo. Terzo capitolo di questa tesi riguarda lo sviluppo di nuovi metodi per la rivelazione di HPV, Chlamydia e Gonorrhoeae in fluidi biologici. Si è scelto un substrato costituito da strips di carta in quanto possono costituire una valida piattaforma di rivelazione, offrendo vantaggi grazie al basso costo, alla possibilità di generare dispositivi portatili e di poter visualizzare il risultato visivamente senza la necessità di strumentazioni. La metodologia sviluppata è molto semplice, non prevede l’uso di strumentazione complessa e si basa sull’uso della isothermal rolling-circle amplification per l’amplificazione del target. Inoltre, di fondamentale importanza, è l’utilizzo di nanoparticelle colorate che, essendo state funzionalizzate con una sequenza di DNA complementare al target amplificato derivante dalla RCA, ne permettono la rivelazione a occhio nudo mediante l’uso di filtri di carta. Queste strips sono state testate su campioni reali permettendo una discriminazione tra campioni positivi e negativi in tempi rapidi (10-15 minuti), aprendo una nuova via verso nuovi test altamente competitivi con quelli attualmente sul mercato.

Um olhar sobre o grou, a felicidade, a neve e o mistério: as quatro irmãs Makioka

O Japão de meados do século XX apresentava um contexto em que influências advindas do ocidente desde a abertura dos portos mesclavam-se à tradição japonesa. Nesse contexto viviam as irmãs Makioka, personagens centrais do romance de Junichiro Tanizaki e objeto principal da presente pesquisa. Por meio da figura de cada uma delas temos acesso ao modo como essas influências adentraram no dia a dia de parte da sociedade japonesa, mais especificamente da família Makioka, tradicional da região de Osaka, e seu círculo social. Para desenvolver esse estudo, faremos a contextualização do período vivido pelo autor e pelas personagens por ele criadas, bem como de que maneira os acontecimentos tiveram participação na formação das mesmas. Também será feita uma análise das personagens secundárias a fim de ampliar a visão acerca das principais. E, finalmente, de acordo com conceitos a respeito da construção de personagem, faremos um estudo das quatro irmãs, levando em consideração aquilo que estava mais na superfície, acessível num primeiro olhar, além dos elementos que compunham o modo de ser de cada uma delas, com as amálgamas e sobreposições resultantes do período.

Robust fitting of Zernike polynomials to noisy point clouds defined over connected domains of arbitrary shape

A new method for fitting a series of Zernike polynomials to point clouds defined over connected domains of arbitrary shape defined within the unit circle is presented in this work. The method is based on the application of machine learning fitting techniques by constructing an extended training set in order to ensure the smooth variation of local curvature over the whole domain. Therefore this technique is best suited for fitting points corresponding to ophthalmic lenses surfaces, particularly progressive power ones, in non-regular domains. We have tested our method by fitting numerical and real surfaces reaching an accuracy of 1 micron in elevation and 0.1 D in local curvature in agreement with the customary tolerances in the ophthalmic manufacturing industry.